If the folders are deleted or Excel file's name is unknown or file's information is overwritten Aidfile Recovery Software can scan the hard drive by file type.

15, December 2016: Recover overwritten files from external hard drive? If the folders are deleted or Excel file's name is unknown or file's information (file's MFT record in NTFS file system, file's Directory entry in FAT32 file system) is overwritten, Aidfile Recovery Software can scan the hard drive by file type.

Tips: If some files are deleted and overwritten in FAT32 file system, Aidfile will provide multiple candidates by file type ID for the same deleted file, give you the maximum extent possible to recover the overwritten files.

http://www.aidfile.com/overwritten-file-recovery.htm

Overwriting is a process of writing a binary set of data in computer data storage and is a term used to describe when new information replaces old information or data. In general it writes over the previous data, hence the name. Overwriting generally occurs when unused file system clusters are written upon with new data, though overwriting is also used in security algorithms. These algorithms use a precise set of rules to remove any part of an original data from the memory by writing a new raw data on the memory.

Data that has been overwritten, even just once, is generally considered to be unrecoverable. There have been theories regarding the feasibility of recovering overwritten data, but none have been put into actual practice. As such there is no evidence in favor of recovering overwritten data, but several suggesting it is entirely impossible.

Use "Full Scan" mode to recover overwritten files from external hard drive if partitions show as "raw" in Windows 7 or recover overwritten files which can not be found with "undelete" and "unformat" and "recover partition", recover overwritten files from raw partition, recover files of partitons which are not NTFS, nor exfat, nor fat32 after showing an error, display as raw file system, unformatted, unknown partition, unpartitioned, needs to be formatted.

External hard disk drives are usually available as pre-assembled integrated products, but may be also assembled by combining an external enclosure (with USB or other interface) with a separately purchased drive. They are available in 2.5-inch and 3.5-inch sizes; 2.5-inch variants are typically called portable external drives, while 3.5-inch variants are referred to as desktop external drives. "Portable" drives are packaged in smaller and lighter enclosures than the "desktop" drives; additionally, "portable" drives use power provided by the USB connection, while "desktop" drives require external power bricks.